Adobe: Flash is open! There's ... Gnash?

Finally, the Flash Platform has a rich developer ecosystem of both open and proprietary tools and technologies, including developer IDEs and environments such as FDT, IntelliJ, and haXe; open source runtimes such as Gnash; and open source video servers such as Red5.
[2010-05-17]

As another Gnash developer, Bastiaan Jacques, wrote on the Gnash mailing list, "Apparently it is sufficient to mention a partial implementation (that does not even support AVM2)."

Moreover, it's an implementation that was created with no help from Adobe:

The SWF file specifications were reverse engineered by others and implemented in Gnash before Adobe published them.

AMF and RTMP were described and implemented elsewhere before Adobe published the specifications.

There are still no proper specifications for the older AVM1, which was reverse engineered for Gnash.

While ECMA script - the basis of ActionScript 3 - has a free implementation, the entire proprietary Flash player API lacks technical documentation.

Adobe uses patent-encumbered codecs such as H.264 and AAC that hinder the distribution of Gnash in some countries.

Neither should we forget that rtmpget received a takedown notice from Adobe for implementing part of the Flash specifications.